How to integrate Material UI into Svelte project - material-ui

Question

I want to integrate Material UI into my Svelte project.
I tried to follow the official documentation from here, but I don't know why I'm getting a strange error while trying to run my project:
loaded rollup.config.js with warnings
(!) Unused external imports
default imported from external module 'rollup-plugin-postcss' but never used
rollup v1.27.13
bundles src/main.js → public/build/bundle.js...
[!] Error: Unexpected token (Note that you need plugins to import files that are not JavaScript)
src/views/App.css (1:0)
1: .footer.svelte-1xl6ht0{position:fixed;left:0;bottom:0;width:100%;background-color:#569e3e;color:white;text-align:center;height:15px}.footer.us.svelte-1xl6ht0,.footer.europe.svelte-1xl6ht0,.footer.central.svelte-1xl6ht0,.footer.south.svelte-1xl6ht0,.footer.apac.svelte-1xl6ht0,.footer.baldr.svelte-1xl6ht0{background-color:#ca4a4a}.footer
....
The problem seems to be related to CSS.
In my src directory I have a directory called theme which contains a file called _smui-theme.scss and this is the content of the file:
#import "#material/theme/color-palette";
// Svelte Colors!
$mdc-theme-primary: #ff3e00;
$mdc-theme-secondary: #676778;
// Other Svelte color: #40b3ff
$mdc-theme-background: #fff;
$mdc-theme-surface: #fff;
$mdc-theme-error: $material-color-red-900;
And here is my rollup.config.json file:
import svelte from 'rollup-plugin-svelte';
import resolve from 'rollup-plugin-node-resolve';
import commonjs from 'rollup-plugin-commonjs';
import livereload from 'rollup-plugin-livereload';
import { terser } from 'rollup-plugin-terser';
import json from '#rollup/plugin-json';
const production = !process.env.ROLLUP_WATCH;
export default {
input: 'src/main.js',
output: {
sourcemap: true,
format: 'iife',
name: 'app',
file: 'public/build/bundle.js',
},
plugins: [
json(),
svelte({
// Enables run-time checks when not in production.
dev: !production,
// Extracts any component CSS out into a separate file — better for performance.
css: css => css.write('public/build/bundle.css'),
// Emit CSS as "files" for other plugins to process
emitCss: true,
}),
resolve({
browser: true,
dedupe: importee => importee === 'svelte' || importee.startsWith('svelte/')
}),
commonjs(),
// In dev mode, call `npm run start` once the bundle has been generated
!production && serve(),
// Watches the `public` directory and refresh the browser on changes when not in production.
!production && livereload('public'),
// Minify for production.
production && terser()
],
watch: {
clearScreen: false
}
};
function serve() {
let started = false;
return {
writeBundle() {
if (!started) {
started = true;
require('child_process').spawn('npm', ['run', 'start', '--', '--dev'], {
stdio: ['ignore', 'inherit', 'inherit'],
shell: true
});
}
}
};
}

Answer 1

In order to solve this issue a postcss plugin is needed for rollup.
I have also added a svelte preprocessor (I think this is optional, but I wanted to be sure).
Make sure you install this packages with npm or yarn:
rollup-plugin-postcss and svelte-preprocess
Then the plugins should be added in rollup.config.js like this:
import svelte from 'rollup-plugin-svelte';
import resolve from 'rollup-plugin-node-resolve';
import commonjs from 'rollup-plugin-commonjs';
import livereload from 'rollup-plugin-livereload';
import { terser } from 'rollup-plugin-terser';
import postcss from 'rollup-plugin-postcss'; <<<------------- Add this
import autoPreprocess from 'svelte-preprocess'; <<<------------- Add this
import json from '#rollup/plugin-json';
const production = !process.env.ROLLUP_WATCH;
export default {
input: 'src/main.js',
output: {
sourcemap: true,
format: 'iife',
name: 'app',
file: 'public/build/bundle.js',
},
plugins: [
json(),
svelte({
// Enables run-time checks when not in production.
dev: !production,
// Extracts any component CSS out into a separate file — better for performance.
css: css => css.write('public/build/bundle.css'),
// Emit CSS as "files" for other plugins to process
emitCss: true,
preprocess: autoPreprocess() <<<------------- Add this
}),
resolve({
browser: true,
dedupe: importee => importee === 'svelte' || importee.startsWith('svelte/')
}),
commonjs(),
postcss({ <<<------------- Add this
extract: true,
minimize: true,
use: [
['sass', {
includePaths: [
'./src/theme',
'./node_modules'
]
}]
]
}),
// In dev mode, call `npm run start` once the bundle has been generated
!production && serve(),
// Watches the `public` directory and refresh the browser on changes when not in production.
!production && livereload('public'),
// Minify for production.
production && terser()
],
watch: {
clearScreen: false
}
};
function serve() {
let started = false;
return {
writeBundle() {
if (!started) {
started = true;
require('child_process').spawn('npm', ['run', 'start', '--', '--dev'], {
stdio: ['ignore', 'inherit', 'inherit'],
shell: true
});
}
}
};
}
Now everything should be working right with the css and Material UI can be used.